Radio telegraph and telephone transmitting system



Sept. 9, 1930. F. e. SIMPSON 1,775,327

RADIO TELEGRAPH AND TELEPHONE TRANSMITTING SYSTEM Original Filed April 2, 1923 INVENTOR ifeaeud flaw) 2240.204

ATTORNEY Patented Sept. 9, 1930 UNITE; sri TES PATENT orrics i FREDERICK GRANT SIMPSON, or

sserrnn, wesnrusron, ASlSIGE-OR, BY Mnsnnris- SIGNMENTS, TO PACIFIC RADIO COMEANY, QF SAN FRANCISCO, CALIFORNIA, A COR- PORATION OF CALIFORNIA R DIO TELEGRAPH Ann rsrnrnonn TRANSMITTING si srnivr Application filed April 2, 1923, serial No. 639,479. Renewed my 19, 1228.

' ing to' createand modulate electromagnetic waves'of a kind suitable for transmission to, and wherein the modulations may be detected and interpreted at, a distant receiving station; The inventionembodies new means ot accomplishing the results mentioned;

his to be noted that I have included in my improved arrangement of circuits, certain lrnown circuits and combinations of electrical apparatus, in an elen'ientary way, to

W15 the extentthat I have embodied therein, to

gether with other known elementary circuits and "devices, a circuit which includes two three electrode electron tubes (or their equivalent, one five electrode electron tube.)

lt also embodies an inductanceand' capacitance, in parallel, connectedin series with a. local generator of electric current. All of which have been shown in my prior Patent Number 1.507 ,689, issued Sept. 9, 192a. I depart, however, from previous use of these known circuits by combining them together, in association with other electrical apparatus, and in adjusting their constants, in a manner which couvertsenergy, locally generated in the form of an electric current, into energy in the form, of electro-magnetic waves, wherein novel means are also provided for modulating the dimensions of such electromagnetic waves to accord with mcdrilations in locally applied forces, as will be understood from the following description in connection with'the accompanying drawings In carrying out the above objects I prefer ably employ a, form of converter of electric current embodying two three electrodeelectron valveslor their equivalent, each having a separate control member, usually that electrode termed the grid, but which may be any element of thevalve which controls the conductivity of the valve, and provide, in connection withsaid electron valves, means for impressing electric potential diiierences between the respective control members of said "electron valves to modulate the converted electric current.

in the order given, with in series between the switch 13 of a triode 10. A variable condenser 9 is In this description I shall designate as triodesr, three electrode electron tubes, each embodyingan evacuated vessel containing a hot cathode, an anode in the form of a plate or concentric cylinderand another electrode placed in a position with respect to the cathode and anode, such that variations in its electrical potential with respect to either of the other two electrodes will cause like variations in the electric current between them.= I shall designate the anode of each triode as the fplate the cathode as the filament and the third electrode as the rid r: i a

In the drawings Figure 1. illustrates, diagrammatically, a form of arrangement of the transmitting circuit'and electrical apparatus at a radio communication station. Figure 2 represents a similar arrangement modified to permit the radiating part of the circuit to be inductivelycoupledto the remalnder of thecircult', instead of directly coupled as shown n F igure 1. i

Like reference numerals designate like parts throughout the severalviews.

Referring particularly to Fig. 1, the numeral 1 represents the ordinary elevated part of'an antenna, at a radio transmitting Pit 2t tion, which is electrically connected in series,

tance coil 3, inductance coil 5, switch 4, con denser 6, to the ground, or counterpoise 7. T he switches 2 and 4 are preferably mechanically actuated by a single control member,

not shown, common to both of them and so ad usted that the active part of eaclrof the coils 3 and 5 shall be of equal in ductance. A

variable condenser 8 is electrically connected 2 and the grid electrically connected in series between the switch 4 and the grid 130i another triode 11. The plate 12 of the triode 10 is electrically connected to theswitch l. The plate 12 of the triode 11 is electrically connected to the switch 2-.

30 is the primary coil of an audio frequency transformer, having a core 29, of anagnetic material, and a secondary coil 28. One terminal of the secondary coil 28 is electria switch 2, induccally connected to the grid 13 of the triode 10. The other terminal of coil 28 is electrically connected to the grid 13 of triode 11. One terminal of the secondary coil 28 is electrically connected to one terminal of a switch 40 the other terminal of which is electrically connected to one of the contacts of a key switch 30; the other Contact of the key switch 39 is electrically connected to the remaining terminal of the secondary coil 28. 'The nor mal position of the key switch 39 is such that its contacts close the circuit with which they are associated. 31 represents telephone transmitter. or a key actuated buzzer, or any device which may function in similar manner. For the purposes of this description I shall refer to 31 as the telephone, except as I may more specifically define it. 32 is a battery or any other generator of electric current. The telephone 81 and the battery are electrically connected in series with .lICll other and with the primary coil 30.

The filament 191-, of the triode 10, has one of its terminals electrically connected to one of the terminals of the filament 14, of the triode 11. The other terminal of :tilainei l 1.4, of triode 10, is electrically connected to one terminal of the rheostat 1?. The other terminal of filament 1d, of triode 11, is electrically connected to one tern'iinal of the rheo- SLllt 17. A battery, or other generator of electric current, 19, has its negative terminal electrically connected to the common terminal of the filaments 141; The positive terminal. of the battery is electrically connected to the rheosttts 15 and 17 by means of the switches 10 and 1.8 respectively. The negative terminal of the battery 19 is also electrically connected to the negative terminal, Ell. of a battery, or other generator of electric current, 24:. An inductance coil 26 is electrically connected in series between the positive terminal of the battery 2% and the common terminal of the inductance coils 3 and 5. it variable condenser 27 is electrically connected in parallel with the inductance coil 26. A condenser is electrically connected in parallel with the battery 2%. A condenser 35 and induct ice coil 20 are electrically connected in series, between the grid 13, of the tri ode 10, and the terminal 34-v of the battery 24. A switch 30 is electrically connected in parallel with the condenser A condenser 37 and an indu -.ta1n:e coil 92 are electrically connected in series between the grid 13. of the triode 11, and the terminal 34: of the battery 2 1-. A switch 38 is electrically connected in parallel vith the condense 37. The inductance coils 20 and 22 have cores 21 and 23 respectively, preferably of iron, or steel, of laminated structure. Coils 20 and 22 should each have sufficient impedance to reduce radio frequency currents which might ol'lie wise be established therein to a. negligible value. I. have found it to be entirely satisfactory to provide coils 20 and 22 each having impedance substantially equivalent to that of each of the triodes 10 and 11 (between plate and filament) at all radio frequencies commonly employed. The secondary coil 28 should have impedance of approximately the same value as that of each of the coils 20 and The condensers 35 and 37 should be of equal capacitance, t 1e value of which may be established within a relatively wide range of values. Condensers and 37 each of one microfarad CilpRClltlnCG have been found to be satisfactory. Condenser 25 may vary in capacitance within a wide range of values. I have found a condenser 25 of 0.5 microfarads capacitance to be suitable for the purpose of this invention when using a variable condenser 27 having a maximum capacitance of 0.005 microfarzuls. An inductance coil 20 of 14 milihenrys, direct current resistance of 10 ohms, and negligible capacitance has been found to be satisfactory when used in connection wi d1 :1 variable condenser 27 having maximum capacitance of 0.005 microfarads.

l have found it possible to substitute fixed condensers for the variable condensers 8 and 9, each fixed condenser having approximately 0.001 microfarads capacitance. I prefer however to use variable condensers 8 and 9 each having a maximum capacitance of 0.001 n 'crofarads. The ditl'erence of potential generated between the terminals of the battery 24 together with tlie ten'lperature of the filaments l lshould be fixed at values largely established by the structural parameters of the triodes 10 and 11. The triodes 10 andll, should be so constructed, with respect to kind and relative spacing of their electrodes as to render them suitable for operation under conditions established by the poivr represented by the electro-magnetic waves generated by my transmitting system. lVith this end in View the design and construction of the triodes may accord with well known principles governing the construction of triodes in general; as l have determined by using triodes designed for use in connection with other well known systems of approximately the same power out-put value as that involved in my experiments. The difference of potential generated between the terminals of the battery 32 should be limited to that suitable for most efficient operation of the telephone 31, or of such other device as may be used in place thereof.

In the operation of this arrangement of circuits the rheostats 15 and 17 should be adjusted, by means of the switches 16 and 18 respectively, to establish a current in each of the filaments 14, of the triodes 10 and 11, just sufficient to fix the temperature of the filaments at a value suitable for the best operation of the triodes with respect to the power represented by the electro-magnetic waves to be generated. If maximum power outputisdsired the switches 36 and 38 should be closed, thereby short-circuiting the condensers 35 and 37 respectively. The

27 should be adjusted to render the compound circuit which includes the battery 24; and

condenser 25 (in parallel) the coil-Q26 and condenser 27 in parallel) the coilS, switch 2 and plate .12, of triode 11,.in parallel with thecoil, switch s and plate 12, of triode the filaments of the trindes lOand 11 through their common terminal to'the terminal 34 oftheha'tteryQl; resonant at substantially twice the resonant frequency oft-he circuit 1- -Q"3'-5'4 G'Z. (Reference is made to my herein-before mentioned prior Patent Number 507,689 formore extender-l discussion ofthe' principles involved in the relative adjustments of the constants of, similar circuitsf for the production of radio frequency currents, or the maximum reinforcement of such; currents.) The switch 40 should be opened. Current impulses will now he establishedfrom the battery 24 through the condenser to the co1nm()11tern1inal 33 of the coils 3"and' 5. These impulses will alter nately" find a path "through the coils 3 and 5, in the manner which "I have described my herein-before mentioned Patent N'umbet l,507,689, and will constitute, in part, an" alternatingcurrentin the circuit which that circuit is resonant. I shall designatethis current as the radio frequency current. As is well known, apart of the energy represented by theradio frequency current is converted into energy in the form of radiated electro-m'agnetic waves. It is also Well known that variations in'either the frequency or in the amplitude ofthe radio frequency current will produce like variations in the length or amplitude, respectively, of the electromagnetic waves; In the present inventlonlhave provided means of varying theampl-itude of the radiated electro- {magn'etic'waves either by partially modulating such amplitude, as is the case when, speech is-transmitted telephonically, or by interm tan analogous association of triodes-with the circuit discussed. In the present invention the radio frequency current likewise is produced and thereafter sustained by the alternate opening and closing of the plate to filament paths in the triodes l0 and 11, since the conductivity of these paths is a function of the electrical potential of the grids 13 with respect to the filaments l4: and the current therein is new function of theelectrical potential of the plates 12 with respect to the filaments l l, considering that the electrical differences of potential mentioned are produced 'by, and have the same period as, the

radio frequency differences of potential be- A tween the points in the circuit 1235 467 with which the t'ricallly connected. a a v From the preceding description it will be seen that thevalves 1.0 and 11, with their associated circuits, may be aptly designated as being in reciprocative association as such provides means for producing and, thereafter, directly sustaining and reinforcing an alternating current by a reciprocatingaction. Mere specifically, the means DIBIIiJIODB Cl coni sists, in part oftwo electron valves so arranged, electrically, with respect to their associated circuits, as to permit the passage of :1- directly sustaining, or reinfor'cing,current between the cathode and anode of each re 'spective valve, only during alternate periods of time, thecontrol members and anodes of the said valves being so associated with an oscillatory circuit,in which said alternating current is resident and, in part wherein, said dlrectlysustainlng or remforcmg, current is also. resident in the form of a pulsating. curgrids I 18 are elecrent, as to determine, and limit, the timepe} riods of maximum conductivity of each valve alternately;the said time periods with 1 respect to one of said valves,being limited "tothe time periods of the positive half cycles of said alternating current in said oscillatory circuit, and, with respect to the other of "saidvalves, to the time periods of the nega tive half cycles the" said alternating current. In this arrangement the Valves, and circuits, each positive pulse of the di' rectly sustaining, or reinforcing, current directly reinforces -one,.and one only, cle of the said alternating current, and each of said half'cycles is,jin this way, reinforced.

I shall hereinafter, in the claims, designate the means herein described, as electron valves in reciprocative association. a

' It is to he noted that the pulses of current, supplied by the battery 24, are effective in reinforcing, and thereby sustaining, the radio 1 frequency current in circuit 123-5-4l-,

67 in proportion to their-amplitude and to their agreement in phase with the radio frequency current. If these pulses of current are caused to pass, in their entirety, n1- ternately through coils 3 and 5and in phase with the radio frequency current simultanecussed be approximated.

ously existent in the coil through which they pass, there will, for a given pulse amplitude, be maximum reinforcement of the radio frequency current. To fully accomplish this result it is requisite that the plate to filament paths of the triodes l and ll shall alternately open and entirely close. It is evident that the greater the difference between the conductivity of the plate to filament path of the triode which is open and that of the same path in the triode which may be but partially closed, at the moment of maximum pulse, the more nearly will the result dislt is known that the conductivity of the plate to filament path of a. triode increases, within certain limits, as the electrical potential of the grid becomes more positive with respect to the filament of the triode, and, conversely, decreases as the grid becomes more negative in its electrical potential with respect to the filament. In the drawing, Fig. 1, it may be clearly seen that there can be no appreciable diii'erencc of electrical potential between the filaments M, of the triodes l0 and 11, as these filaments are electrically connected together having one terminal common to both of them. Variations, therefore, in the difference of clecJrical potential between the grid 13, of the triode l0, and the grid 13, of the triode 11, will react upon the alternating conductivities of the plate to filament paths of the triod'es and consequently, upon the degreeof reinforcement, by the pulses of current supplied by the battery 24:, of the radio frequency current in the circuit 1-23-5-l-(3-7. Variations of electrical potential difference between the grids 13, of the tri-odes 10, and 11, will in the manner explained therefore produce proportional variations in the amplitudes of the radio frequency current in the circuit 1-23-5-%-37 and in the energy represented by the electro-magnetic waves radiated by that circuit.

If it is desired to transmit speech, or other sounds, sound waves impressed upon the diaphram of the telephone 31 will cause variations of electric current in the primary coil 30, as is well known these variations will, by means of the inductive associc tion of the coil with the secondary coil 28, produce alternating potential differences, between the terminals of the latter coil, of the same frequency as that of the sound waves; these potential differences will establish an electric current having two principal components, one of which will reside in the circuit 28- 36-20 22 38 and the other alternately in the circuit 28-triode 10, (grid 13 to filament I l) 2238 and in the circuit 28triodes 11 (grid 13 to filament 14:) 2036. The latter component alternates between the two last defined circuits, due to the uni-directional conducting property of the grid to filament paths of the triodes, at the voice, or audio,fre-

quency of the current. Due to the combined effect of these audio frequency currents, there is impressed between the grids 13, of the triodes 10 and 11, variations of differ ences of electrical potential of the same frequencies and of proportionate amplitudes. These variations of electrical potential cause like variations in the energy represented by the radiated electro-magnetic waves in the manner hereinbefore described.

If it is desired to transmit by telegraph, the signals consisting of long and short groups of wave trains, a key operated buzzer, or other similar device, may be substituted for the telephone 31. The phenomena appertaining to this method of operation is the same as that described in connection with the transmission of sound, except that the sound frequency modulations are replaced by the frequency of interruption of the current, in the primary coil 30, as caused by the action of the buzzer, during the periods in which it is active, as determined by the manipulation of its controlling key.

If it is desired to transmit by telegraph, the signals consisting of uninterrupted wave trains of various l ngths, the switch should be closed. The grids 13 are now electrically connected to each other by means of the closed switch 40 and the key switch 39, which is in its normal, closed, position, and there is negligible difference of electrical potential between them. Under this condition there will be no appreciable reinforcement of the radio frequency current, in the circuit 12 3-5-4l-6-7, and it will immediately cease.

l'f now the key switch 39 be depressed it will open the low impedance electrical connection between the grids, introducing the high impedance coil 28 in place thereof, and the radio frequency current, above mentioned, will be re-established. Signals may, therefore, be transmitted of the desired kind by manipulating the key switch 39.

I have found it possible to operate my present arrangement of circuits in all of the ways herein-before described, but at greatly reduced power output, by opening the switches 36 and 38 and thereby introducing the condensers 35 and 37 respectively into the previously described circuits in place of the switches mentioned. Condensers 35 and 37, when introduced into the circuits in the manner shown, become reservoirs, or traps, tending to check that component of the audio frequency current which finds a circuit alternately between the grid and filament of triode 10 and the grid and filament of triode 11, as herein-before described. I have found the introduction of condensers 35 and 37 into the circuits, as shown, to be desirable for the purpose of reduction of the power represented by the radiated electro-magnetic waves. It may be readily understood that the introduction of these condensers, in the manner shown but only at greatly reduced power.

appended claims.

and described, lowers the eifective reactance between the grids 13 and therefore limits the maximum difference of electrical potential between them and, consequently, limits the degree of reinforcement of the radio frequency current possiblewhen they are so introduced.

I have found it to be possible to operate my present arrangement of circuits, modified by the removal of condensers 35 and 37, the switches 36 and 38, and the coils 20 and 22; In the latter instance there is no audio frequency current produced by the audio frequency potentials at the terminals of the secondary coil 28. These potentials are, however, impressed between the grids 13 and cause modulations in the radio frequency current as hereinbefore described. The radio frequency currentis limited in its amplitude by the effectof charges retainedby the condensers 8 and 9 due to the uni-directional conducting prop erty of the triode grid to filament paths; such chargesoperating to reduce the difference of potential between. the grids.

Referring to Fig. 2, 1 represents the ordinary elevated part of an antenna, at a radio transmitting station, which is electrically connected in series with the switch 42, the inductance coil 41, to the ground, or counterpoise, 7. The variable condenser l3 has its tor minals electrically connected to the switches 52 and 4 respectively. The inductance coil ll is in variable inductive association with the inductance coil 3. The remainder of this figure is the same as that of Fig. 1. f

In the operation of this arrangement of circuits the same methods are employed and the same phenomena are created thereby as those described in connection with Fig. 1; except that it is necessary to adjust the circuits condition of resonance at the frequency of the radio frequency current desired. This condition is attained by adjusting the switches 42, 2 and 4:, the condenser 43 and the coupling between the coils 41 and 3.

It is obvious that many other modifications, or changes, in the shape, kind and arrangement of the various parts may be made without departing from the broad scope of the As an example, it is clear that the action herein described may be obtained by substituting one electron'tube having a single filament, two grids and two plates for the triodes lOand 11. It may also be seen that other electric valves operating in'a manner similar to the triodes may be used. It is further apparent. that my arrangement of circuits and combinations of electrical apparatus may be used for many purposes, wherein modulation, or interruption, of an alternating electric current'is desired, other than those described herein.

While Ihave shown various forms and kinds of apparatus thereof, what I claim as new and useful, and

by Letters Patentis 1. The combination with a converter of electric current embodying two electron of iny owninvention, and desire to secure valves in reciprocative association arranged tdconvertdirect current into a single alternating current only, of modulating means connected with the respective controlmembers of said two valves and arranged to modulate converted electric current by impressing electric potential differences between said two control members and electric circuits, provided with grouped inductance, external to said electron valvesand external to the source of said modulating potentials affording means for the passage of by said, electric potential differences.

2.The combination with a converter of electric current embodying two electron valves in reciprocative association arranged toconvert direct current into a single alter nating current only, of means for modulating the converted current fromsaid converterby the application of external forces, said means including devices for impressing electric potentlal dlfferencesproduced by said external forces-between the respective control mem bers of'said two electron valves and circuits, having grouped inductance external to the source of said modulating potentials and grouped capacitance external to said electron valves affording means for the passage of electric currents produced by said electric potential differences.., i

3. system for generating a one-frequency alternating current modulated at lower fre quency comprising an oscillatory circuit, a source of direct current connected thereto through a pair of readily variable resistance gaps responsively sensitive to both frequencies, resistance influencing means associated with said gaps, said means being so excited by current flow in said circuit as to influence said gaps oppositely whereby alternating cur rents are generated in said circuit, and a source of lower frequency modulating current connected directly to said gap influencing means to also excite said influencing means oppositely.

4. A system for generating a one-frequency alternating current modulated at lower freqency comprising oscillato y circuit, a

electric currents produced source of direct current connected thereto through the filament-to-plate paths of a pair of three-electrode vacuum tubes connected in parallel relation to opposite sides of a reactance element in said circuit, reactance means connecting the grid electrodes of said tubes to opposite sides of said reactance element in said circuit, and a source of lower frequency modulating current connected to said grid electrodes.

5. A system for generating a one-frequency alternating current modulated at lower frequency comprising an oscillator circuit having a pair of substantially equally reacting inductance coils non-inductively related and a condenser, a source of direct current connected to said circuit at a point between said coils and to opposite sides of said condenser by way of the filament-to-plate paths of a pair of three electrode vacuum tubes, reactance means connecting the grid electrodes of said tubes to said oscillating circuit at opposite sides of said condenser, and a source of lower frequency modulating current connected between said grid electrodes.

6. A system for generating a one-frequency alternating current modulated at lower frequency comprising an oscillatory circuit, a

source of direct current connected thereto through a pair of readily variable resistance gaps responsively sensitive to both frequencies, means for influencing the resistance of said gaps intimately associated therewith, reactance means directly connecting said gap influencing means to said oscillatory circuit, so that the influencing means are excited by current flow in said circuit in a direction so as to influence said gaps oppositely whereby current flow from said direct current source is commutated to create alternating currents in said oscillatory circuit, and means directly connected to said gap influencing means for simultaneously applying lower frequency modulating current effects directly to said gap influencing means for additionally infiuencing the resistance of said gaps.

FREDERICK GRANT SIMPSON. 

